<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{
            background: #000;
        }
        #snow{
            position: fixed;
            left: 0;
            top: 0;
            right: 0;
            bottom: 0;
            background: url('img/snow.png'),  url('img/snow2.jpg');
            -webkit-animation: snow 15s linear infinite;
            animation: snow 15s linear infinite;
        }
        @keyframes snow{
            0% {
                background-position: 0 0, 0 0;
            }
            100% {
                background-position: 500px 1000px, 500px 500px;
            }
        }
        @-webkit-keyframes snow{
            0% {
                background-position: 0 0, 0 0;
            }
            100% {
                background-position: 500px 1000px, 500px 500px;
            }
        }
    </style>
</head>
<body>
<div id="snow">*</div>
</body>

</html>